1. Field of the Invention
The invention relates to a universal frame for electric bikes and human powered bicycles and, more particularly, to a bicycle frame universal for electric bikes and human powered bicycles, to thereby simplify the process and reduce the amount of inventories effectively, and achieve the convenience of universal interchangeability.
2. Brief Description of the Related Art
A conventional bicycle frame 9 is shown in FIG. 1, the bicycle frame 9 is consisted of a top tube 91, a down tube 92, a seat tube 93, two seat stays 94 and two chain stays 95, wherein a bottom bracket shell 96 is welded on the junction of the down tube 92 and the chain stays 95, the bottom bracket shell 96 is provided for assembling a main-shaft-chain wheel set (the main-shaft-chain wheel set is a prior art structure and not shown in figure). It is a basic structure of a conventional human powered bicycle. However, with the advances in technology, one kind of electric bike is invented for reducing physical burden of riders. In this kind of electric bike, the main-shaft-chain wheel set is connected to a tube motor for being transmitted by electric power, such as related patent applications EP1878650B1. Since the tube motor is not the feature of the present invention, no more detail here. For the manufacture of bicycle frames, the problem is that the specification of the bottom bracket shells 96 of human powered bicycle and electric bikes are different and cannot be universal. The manufacture have to weld different bottom bracket shells 96 on the same bicycle frame 9 depending on different use requirements (electric bikes or human powered bicycles). Thus, not only increase the inconvenience of the process and make inventory increased greatly, but also affect the sales willingness of bike shops, which should furnish double products in limited store space.